Example command of add_event not representative enough

[yytan25]

When I input an invalid command format for add_event, I received the following message, which contains an example command:

However, when I tried to enter the example command into the CLI, I received a message as follows:

While this date validity check is absolutely necessary for this feature, it may cause frustration for new users, who wish to get the hang of the product. Hence I suggest that the example date be sometime which will be later, so that the error message above will not be shown.